Display control apparatus, display control method, and image capturing apparatus

ABSTRACT

A display control apparatus, comprises: a focus detection unit configured to detect, based on an image signal obtainable from an image sensor, a focus state and reliability of the image signal; and a display control unit configured to display in a display unit, when focus adjustment is performed by a manual operation, an index that indicates the focus state that was detected by the focus detection unit, wherein the display control unit changes a display format of the index according to the reliability.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display control apparatus providedwith a configuration that detects a focus state and a configuration thatcontrols display of the focus state, and a display control method, andan image capturing apparatus.

2. Description of the Related Art

A focus control apparatus of a high definition video camera or the likethat is compatible with recent full HD, 4K, or the like has higherresolving power than ever before, and so when a photographer focuses ona subject using a manual focus operation (ME operation), it is not easyto focus exactly. In particular, when performing a focus operation whilechecking focus using a viewfinder, a display panel, or the like providedin the camera, there are cases where focus offset occurs to a degreethat cannot be checked with the viewfinder, the display panel, or thelike, and thus it is difficult to judge whether or not an intended focusstate has been established.

Consequently, a focus assist method that assists an MF operation hasbeen proposed. Japanese Patent Laid-Open No. 2007-248615 proposes amethod in which when performing an MF operation, a focus stateevaluation value is calculated, and a degree of focus state is displayedin a bar display. Also, Japanese Patent Laid-Open No. 2005-140943proposes, as focus assist methods in an image capturing apparatus, aplurality of display methods that indicate changes in focus stateaccompanying movement of a focusing lens.

On the other hand, Japanese Patent Laid-Open No. 2001-083407 describesan image capturing apparatus utilizing an on-imaging plane phasedifference detection method as a method for detecting the focus state,and in this image capturing apparatus a live view mode is considered inwhich image shooting is performed while displaying a shot image on arear monitor or the like.

However, in a case where, as in Japanese Patent Laid-Open No.2001-083407, focus detection is performed using an on-imaging planephase difference detection method in an image capturing apparatuscapable of image display in a live view mode, phase difference isdetected on the imaging plane, so detection accuracy decreases accordingto a blur state of the subject.

For example, when a subject image as shown in FIG. 12A was shot, in apair of signals used in the phase difference detection method, twopeak-like shapes are seen in the vicinity of being in focus, as shown inFIG. 12B. Also, in the vicinity of being in focus, where reference sign1201 denotes an A image and reference sign 1202 denotes a B image, the Aimage 1201 and the B image 1202 have about the same shape. Accordingly,by applying the phase difference detection method and calculating theoffset amount of these two images, it is possible to calculate a defocusamount with high detection accuracy.

On the other hand, when focus is greatly blurred (large blur), forexample, as shown in FIG. 12C, the two mountain-like shapes collapse,becoming one mountain-like shape. Further, that mountain-like shape hasa broad base, and the shape differs between the A image 1201 and the Bimage 1202. Therefore, in a large blur state, the degree of coincidenceof the A image and the B image worsens, so detection accuracy decreases.

Detection accuracy also decreases depending on aperture. The reason forthis is that, even if distance to the subject is the same, as theaperture changes from a full-open aperture to a small aperture, theoffset amount of the A image and the B image decreases and resolvingpower in phase difference detection becomes more coarse. Also, whenthere is low illuminance, the S/N ratio decreases, and so the detectionaccuracy decreases.

As described above, the accuracy of focus detection by an on-imagingplane phase difference detection method differs depending on the imageshooting state, so when performing focus assist display, there are caseswhere it is not possible to display stable information. In addition,there are some cases where a user may feel uncomfortable when performingfocus adjustment while monitoring information display due to differencesin focus ring operability and in the depth of focus determined by thefocal length of an attached lens.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the abovesituation, and realizes a focus assist function that is stable whenperforming manual focus adjustment.

According to the present invention, provided is a display controlapparatus, comprising: a focus detection unit configured to detect,based on an image signal obtainable from an image sensor, a focus stateand reliability of the image signal; and a display control unitconfigured to display in a display unit, when focus adjustment isperformed by a manual operation, an index that indicates the focus statethat was detected by the focus detection unit, wherein the displaycontrol unit changes a display format of the index according to thereliability.

Furthermore, according to the present invention, provided is an imagecapturing apparatus, comprising: an image sensor having a plurality ofpixels provided with a plurality of photoelectric converters for asingle microlens, the image sensor receiving luminous flux incidentthrough an imaging optical system with the plurality of photoelectricconverters and outputting a pair of image signals; and a display controlapparatus that comprises: a focus detection unit configured to detect,based on the pair of image signals output from the image sensor, a focusstate by performing focus detection using a phase difference method andreliability of the pair of image signals; and a display control unitconfigured to display in a display unit, when focus adjustment isperformed by a manual operation, an index that indicates the focus statethat was detected by the focus detection unit, wherein the displaycontrol unit changes a display format of the index according to thereliability.

Further, according to the present invention, provided is a displaycontrol method, comprising: performing focus detection to detect, basedon an image signal obtainable from an image sensor, a focus state andreliability of the image signal; and performing display control todisplay in a display unit, when focus adjustment is performed by amanual operation, an index that indicates the focus state that wasdetected in the focus detection, wherein in the display control, adisplay format of the index is changed according to the reliability.

Further, according to the present invention, provided is acomputer-readable storage medium storing a program for causing acomputer to execute a display control method, comprising: performingfocus detection to detect, based on an image signal obtainable from animage sensor, a focus state and reliability of the image signal; andperforming display control to display in a display unit, when focusadjustment is performed by a manual operation, an index that indicatesthe focus state that was detected in the focus detection, wherein in thedisplay control, a display format of the index is changed according tothe reliability.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the description, serve to explain the principles of theinvention.

FIG. 1 is a block diagram that shows a schematic: configuration of animage capturing system according to an embodiment of the presentinvention;

FIG. 2 is a schematic view of a pixel array of an image sensor accordingto an embodiment;

FIGS. 3A to 3D show an example of focus assist display according to afirst embodiment;

FIGS. 4A and 4B illustrate a flowchart that shows a main flow of focusassist display control according to the first embodiment;

FIG. 5 is a flowchart that shows focus detection processing according tothe first embodiment;

FIGS. 6A to 6D show an example of a focus detection area and imagesignals obtained from the focus detection area according to the firstembodiment;

FIGS. 7A and 7B illustrate a correlation operation method according tothe first embodiment;

FIGS. 8A and 8B illustrate a correlation operation method according tothe first embodiment;

FIGS. 9A to 9D show a relationship between a defocus amount and adisplay position of an index in focus assist display according to thefirst embodiment;

FIGS. 10A and 10B show a relationship between a focus ring operation andan index of focus assist display according to a second embodiment;

FIGS. 11A to 11C are flowcharts and a table that show processing to setan amount of conversion from a defocus amount to an index position inthe second embodiment; and

FIGS. 12A to 12C show an example of image signals obtained in anon-imaging plane phase difference detection method.

DESCRIPTION OF THE EMBODIMENTS

Exemplary embodiments of the present invention will be described indetail in accordance with the accompanying drawings. Note that theembodiments described, below are only one example of means for realizingthe present invention, and may be revised or modified as appropriatedepending on the configuration of an apparatus where the presentinvention is to be applied or various conditions, and the presentinvention is not limited by the below embodiments.

Configuration of Image Capturing System

FIG. 1 is a block diagram that shows a schematic configuration of animage capturing system provided with a focus assist function accordingto an embodiment of the present invention. Note that in the presentembodiment, an interchangeable lens-type image capturing system isdescribed, but an image capturing apparatus having a fixed lens may alsobe used.

As shown in FIG. 1, the image capturing system in the present embodimentis configured from a lens unit 10 and a camera main body 20. Also, datacommunications are performed between a lens control unit 106 thatperforms unified control of operation of the lens unit 10 as a whole,and a camera control unit 207 that performs unified control of operationof the image capturing system as a whole.

First is a description of the configuration of the lens unit 10. Thelens unit 10 has an imaging optical system configured from a fixed lens101, an aperture 102, a focusing lens 103, a zoom lens (not shown), andthe like. The aperture 102 is driven by an aperture drive unit 104, andcontrols an amount of light incident on an image sensor 201, describedlater. The focusing lens 103 is driven by a focusing lens drive unit105, and is used for focus adjustment. An unshown zoom lens is driven bya zoom lens drive unit, and is used for zoom adjustment. Note that inthe present embodiment, the zoom lens and the zoom lens drive unit arenot essential configurations, and may be omitted.

The aperture drive unit 104, the focusing lens drive unit 105, and thezoom lens drive unit are controlled by the lens control unit 106, andthus an opening diameter of the aperture 102, and positions of thefocusing lens 103 and the zoom lens, are controlled. When a user hasperformed a focus operation, a zoom operation, or the like by operatinga focus ring, a zoom ring, or the like provided in a lens operation unit107, the lens control unit 106 performs control corresponding to theuser operation. The lens control unit 106, according to control commandsand control information received from the camera control unit 207described later, performs control of the aperture drive unit 104, thefocusing lens drive unit 105, and the zoom lens drive unit, andtransmits lens information to the camera control unit 207.

Next is a description of the configuration of the camera main body 20provided with a focus assist function according to the presentembodiment. In the camera main body 20, the image sensor 201 isconfigured with a CCD or CMOS sensor, where luminous flux that haspassed through the imaging optical system of the lens unit 10 is formedas an image on a light-receiving face of the image sensor 201. Also, asubject image that has been formed is photoelectrically converted to anelectric charge according to the incident light amount by photodiodes(photoelectric converters) of the image sensor 201, and accumulated. Theelectric charge that has been accumulated in each photodiode issequentially read out from the image sensor 201 as a voltage signalcorresponding to the electric charge based on a drive pulse conferredfrom a timing generator 209 according to an instruction of the cameracontrol unit 207. Note that while the detailed configuration of theimage sensor 201 will be described later, the image sensor 201 in thepresent embodiment, other than ordinary image signals, can output a pairof focus detection signals that can be used for focus detection by aphase difference method.

An image signal and a focus detection signal that have been read outfrom the image sensor 201 are input to a CDS/AGC circuit 202, andcorrelated double sampling for removing reset noise, gain adjustment,and signal digitization are performed. The CDS/AGC circuit 202 outputs aprocessed image signal to a camera signal processing unit 203, andoutputs a focus detection signal to a focus signal processing unit 204.

The camera signal processing unit 203 performs various image processingon an image signal that has been output from the CDS/AGC circuit 202,and generates a video signal. A display unit 205 is a display devicesuch as an LCD or organic EL display device, and displays an image basedon the video signal that was output from the camera signal processingunit 203. Also, when in a recording mode in which an image signal isrecorded, the image signal is transmitted from the camera signalprocessing unit 203 to a recording unit 206, and is recorded to arecording medium such as an optical device, a semiconductor memory, or amagnetic tape.

The focus signal processing unit 204 performs a correlation operationbased on a pair of focus detection signals that have been output fromthe CDS/AGC circuit 202 to detect a focus state. Here, a correlationamount, a defocus amount, and reliability information (degree ofcoincidence between two images, steepness of two images, contrastinformation, saturation information, defect information, and the like)are calculated. The calculated defocus amount and reliabilityinformation are output to the camera control unit 207. Also, the cameracontrol unit 207, based on the obtained defocus amount and reliabilityinformation, notifies the focus signal processing unit 204 of a changein settings used to calculate the defocus amount and reliabilityinformation. Note that the details of the correlation operation will bedescribed later with reference to FIGS. 6A to 6D through FIGS. 8A and8B.

The camera control unit 207 performs control by exchanging informationwith each configuration within the camera main body 20. In addition toprocessing within the camera main body 20, the camera control unit 207controls power ON/OFF, settings changes, and recording according toinput from a camera operation unit 208 that was operated by a user.Further, the camera control unit 207 executes various functionscorresponding to user operation such as switching between autofocus (AF)control and manual focus (MF) control, checking recorded video, and thelike. Also, as described above, the camera control unit 207 exchangesinformation with the lens control unit 106 within the lens unit 10,transmits control commands and control information of the imagingoptical system, and obtains information within the lens unit 10.

Image Sensor Configuration

FIG. 2 shows a schematic view of a pixel array of the image sensor 201in the present embodiment. In FIG. 2, a pixel array of a two-dimensionalCMOS sensor used as the image sensor 201 in the present embodiment isshown in a range of four columns×four rows of image capturing pixels (arange of eight columns×four rows as an array of focus detection pixels).

In the present embodiment, a pixel group 200 includes two columns×tworows of pixels, and is covered by a Bayer array color filter. In eachpixel group 200, a pixel 200R having spectral sensitivity to red (R) ispositioned at the upper left, pixels 200G having spectral sensitivity togreen (G) are positioned at the upper right and the lower left, and apixel 200B having spectral sensitivity to blue (B) is positioned at thelower right. Further, in the image sensor 201 of the present embodiment,in order to perform focus detection by an on-imaging plane phasedifference method, each pixel holds a plurality of photodiodes(photoelectric converters) for one microlens 215. In the presentembodiment, each pixel is configured with two photodiodes 211 and 212arranged in two columns×one row.

By having many pixel groups 200, each including two columns×two rows ofpixels (four columns×two rows of photodiodes) shown in FIG. 2, arrangedon the imaging plane, the image sensor 201 is enabled to obtain imagesignals and focus detection signals.

In each pixel having this sort of configuration, luminous flux is splitby the microlens 215 and formed as an image on the photodiodes 211 and212. A signal (A+B signal) obtained by adding signals from the twophotodiodes 211 and 212 is used as an image signal, and two signals (Aand B image signals) respectively read out from the individualphotodiodes 211 and 212 are used as focus detection signals. Note thatthe image signal and the focus detection signals may be respectivelyread out, but in the present embodiment, in consideration of processingload, the following sort of configuration may also be adopted. That is,the image signal (A+B signal), and a focus detection signal from eitherone of the photodiodes 211 and 212 (for example, the A signal), are readout, and by taking the difference between those signals, the other focusdetection signal (for example, the B signal) is obtained.

Note that in the present embodiment, a configuration is adopted in whichin each pixel, there are the two photodiodes 211 and 212 for the onemicrolens 215, but the number of photodiodes is not limited to two, anda configuration may also be adopted in which the number of photodiodesis three or more. Also, a configuration may be adopted in which thereare a plurality of pixels having a different opening position of a lightreceiving portion for the microlens 215. That is, a configuration ispreferable in which, as a result, two signals used for phase differencedetection such that it is possible to detect the phase differencebetween the A image signal and the B image signal are obtained. Also,the present invention is not limited to a configuration in which, asshown in FIG. 2, all pixels have a plurality of photodiodes; aconfiguration may also be adopted in which focus detection pixels asshown in FIG. 2 are discretely provided within normal pixels included inthe image sensor 201.

First Embodiment Display Format of Focus Assist

Next is a description of a display format of focus assist in the presentembodiment, with reference to FIGS. 3A to 3D. In the present embodiment,the types of focus assist display include four display formats fromfirst to fourth display formats, and focus states that were detected areindicated by display parts 301 to 317.

FIG. 3A shows an example of the first display format, and shows a statein which a subject was determined to be in focus. In a state determinedto be in focus, the position of the inward pointing display part 301coincides with the position of the outward pointing display part 302(here, stopped at the top). Also, when determined to be in an in-focusstate, for example, the display part 301 and the display part 302 may bedisplayed in a different color (for example, green) than the color inother display formats (for example, white).

FIG. 3B shows an example of the second display format, in which thesubject is not in focus, and in a case where the reliability of focusdetection results is high, shows the direction to an in-focus positionand the size of a defocus amount. For example, in a case where focus isset to an infinite distance side (rear focus) relative to the subject,in a state with the inward pointing display part 303 stopped at the top,the outward pointing display parts 304 and 305 move with bilateralsymmetry on the circumference. The positions of the display part 304 andthe display part 305 indicate the size of the defocus amount, andindicate a larger defocus amount the further they are separated from theposition of the display part 303 (reference position). Note that thedisplay part 303 corresponds to the display part 301, and a state withthe display parts 304 and 305 overlapping each other corresponds to thedisplay part 302.

On the other hand, in a case where focus is set to a near side (frontfocus) relative to the subject, in a state with the outward pointingdisplay part 306 stopped at the top, the inward pointing display parts307 and 308 move with bilateral symmetry on the circumference. Thepositions of the display part 307 and the display part 308 indicate thesize of the defocus amount, and indicate a larger defocus amount thefurther they are separated from the position of the display part 306(reference position). Note that the display part 306 corresponds to thedisplay part 302, and a state with the display parts 307 and 308overlapping each other corresponds to the display part 301. As describedabove, in the second display format, the size of the defocus amount canbe indicated by the positions of the display parts that move. Also, thedirection to the in-focus position (defocus direction) can be indicatedby the direction in which the display part stopped at the top ispointing.

FIG. 3C shows an example of the third display format, in which only thedirection to the in-focus position is shown in a case where thereliability of focus detection results is moderate. Here, the displayparts 309 to 314 are fixed at predetermined positions regardless of thedefocus amount. Also, in the case of rear focus, the inward pointingdisplay part 309 is fixed at the top, and in the case of front focus,the outward pointing display part 312 is fixed at the top. That is, inthe third display format, the size of the defocus amount is notindicated, and the direction to the in-focus position is indicated bythe direction in which the display part fixed at the top is pointing.

FIG. 3D shows an example of the fourth display format, and shows a casewhere the reliability of focus detection results is low. In this case,both the size of the defocus amount and the defocus direction are notshown, so a user is allowed to see that focus detection is not possible.Here, the display parts 315 to 317 are displayed in a different color(for example, gray) than the color in other display formats, and thedisplay parts 315 to 317 are fixed at predetermined positions. Also, theshapes of the display part 316 and the display part 317 are madedifferent than the shapes in other display formats.

Note that the focus assist display shown in FIGS. 3A to 3D is only anexample, and the present invention is not limited to this display.

Focus Assist Display Control

Next is a description of focus assist display control executed by thecamera control unit 207. FIGS. 4A and 4B illustrate a flowchart thatshows a procedure of main processing of focus assist display controlexecuted by the camera control unit 207. This processing is executed ina predetermined cycle according to a computer program that has beenstored in the camera control unit 207. For example, this processing isexecuted in a cycle of reading out an image signal (each verticalsynchronizing period) from the image sensor 201 in order to generate animage of one frame (or one field). This processing may also be repeateda plurality of times within a vertical synchronizing period.

In step S101 a focus detection area is set, and next, the focus signalprocessing unit 204 confirms whether the focus signal has been updated(step S102). If the focus signal has been updated, focus detectionprocessing is performed in the focus signal processing unit 204 (stepS103). Then, as a result of focus detection processing, a defocus amountand reliability are obtained.

Here, the focus detection processing performed in step S103 will bedescribed with reference to FIGS. 5 to 8A and 8B. FIG. 5 is a flowchartthat shows focus detection processing, and is performed by the focussignal processing unit 204. First, in step S201, the focus signalprocessing unit 204 obtains a pair of focus detection signals from thefocus detection area that was set in step S101. Next, in step S202, acorrelation amount is calculated from the pair of focus detectionsignals that were obtained in step S201. Next, in step S203, acorrelation change amount is calculated from the correlation amount thatwas calculated in step S202. Then, in step S204, a focus offset amountis calculated from the correlation change amount that was calculated instep S203. Also, in step S205, reliability of the focus detectionsignals that were obtained in step S201 is calculated. This reliabilitycorresponds to a reliability that expresses the extent to which it ispossible to rely on the focus offset amount that was calculated in stepS204. Then, in step S206, the focus offset amount is converted to adefocus amount.

Note that the defocus amount may be expressed as an absolute distancefrom the in-focus position, or as a number of pulses necessary in orderto move the focusing lens 103 to the in-focus position, or may be anexpression of a different dimension and units as such an expression, ormay be a relative expression. That is, it is preferable to express thedefocus amount such that it is possible to judge the distance from thein-focus state, or possible to judge how much focus control needs to beperformed to move to the in-focus state.

Next, the focus detection processing described in FIG. 5 will bedescribed in detail with reference to FIGS. 6A to 6D, and FIGS. 7A and7B. FIG. 6A shows an example of a focus detection area 402 that has beenset on a pixel array 401 used to configure the image sensor 201. In anoperation area 404, where focus detection signals necessary forperforming a correlation operation described later are read out, thefocus detection area 402 is combined with shift areas 403 necessary forthe correlation operation. In FIG. 6A, reference signs p, q, s, and trespectively indicate coordinates in the x-axis direction, and theoperation area 404 corresponds to the range from p to q, and the focusdetection area 402 corresponds to the range from s to t.

FIGS. 6B to 6D show an example of focus detection signals that wereobtained from the operation area 404 that was set in FIG. 6A. The rangefrom s to t corresponds to the focus detection area 402, and the rangefrom p to q corresponds to the operation area 404 necessary for thecorrelation amount operation, which is based on a shift amount. Solidline 501 indicates an A image signal, and broken line 502 indicates a Bimage signal.

FIG. 6B shows the A image signal 501 and the B image signal 502 prior toshifting as waveforms. In FIG. 6C, the waveforms of the A image signal501 and the B image signal 502 are shifted in a plus direction withrespect to the positions prior to the shifting shown in FIG. 6B, and inFIG. 6D, the waveforms of the A image signal 501 and the B image signal502 are shifted in a minus direction with respect to the positions priorto the shifting shown in FIG. 6B. When calculating a correlation amount,the A image signal 501 and the B image signal 502 are shifted bit by bitin the directions of the respective arrows.

Next is a description of a calculation method of a correlation amountCOR in step S202. First, as described in FIGS. 6C and 6D, the A imagesignal 501 and the B image signal 502 are shifted bit by bit, and ineach shift state, a sum of absolute values of the difference between theA image signal 501 and the B image signal 502 in the focus detectionarea 402 that was set is calculated. Here, a minimum number of shifts isrepresented by p-s, and a maximum number of shifts is represented byq-t. Also, where the shift amount is represented by i, start coordinatesof the focus detection area are represented by x, and final coordinatesof the focus detection area are represented by y, it is possible tocalculate the correlation amount COR with below expression (1).

$\begin{matrix}{{{{COR}\lbrack i\rbrack} = {\sum\limits_{k = x}^{y}{{{A\left\lbrack {k + i} \right\rbrack} - {B\left\lbrack {k - i} \right\rbrack}}}}}\left\{ {\left( {p - s} \right) < i < \left( {q - t} \right)} \right\}} & (1)\end{matrix}$

FIG. 7A shows an example of change of the correlation amount, in whichthe shift amount is shown on the horizontal axis of the graph and thecorrelation amount is shown on the vertical axis. In a correlationamount waveform 601, reference signs 602 and 603 indicate the vicinityof local minimums. Even within such a vicinity, it can be said that asthe correlation amount decreases, the degree of coincidence of the Aimage signal 501 and the B image signal 502 increases.

Next is a description of a calculation method of a correlation changeamount ΔCOR in step S203. First, a correlation change amount iscalculated from a difference in correlation amounts when skipping oneshift from the correlation amount waveform shown in FIG. 7A. Here, aminimum number of shifts is represented by p-s in FIGS. 7A and 7B, and amaximum number of shifts is represented by q-t in FIGS. 7A and 7B. Wherethe shift amount is represented by i, it is possible to calculate thecorrelation change amount ΔCOR with below expression (2).

ΔCOR[i]=ΔCOR[i−1]−ΔCOR[i+1]

(p−s+1)<i<(q−t−1)  (2)

FIG. 7B shows an example of the correlation change amount ΔCOR, in whichthe shift amount is shown on the horizontal axis of the graph and thecorrelation change amount is shown on the vertical axis. In acorrelation change amount waveform 604, reference signs 605 and 606indicate the vicinity where the correlation change amount changes fromplus to minus. A state where the correlation change amount becomes zeroin the portion 605 and the portion 606 is called a zero cross, and inthis state the degree of coincidence of the A image signal 501 and the Bimage signal 502 is largest, and a focus offset amount can be obtainedbased on the shift amount at that time.

FIG. 8A shows an enlarged view of the portion 605 in FIG. 7B, in whichreference sign 607 denotes a portion of the correlation change amountwaveform 604. A calculation method of a focus offset amount PRD in stepS204 will be described with reference to FIG. 8A. First, the focusoffset amount PRD is divided into an integer portion β and a fractionalportion α. The fractional portion α can be calculated with belowexpression (3), from the relationship of triangle ABC and triangle ADEin FIG. 8A.

$\begin{matrix}{{{{AB}\text{:}{AD}} = {{BC}\text{:}{DE}}}{{{\Delta \; {{COR}\left\lbrack {k - 1} \right\rbrack}\text{:}\Delta \; {{COR}\left\lbrack {k - 1} \right\rbrack}} - {\Delta \; {{COR}\lbrack k\rbrack}}} = {{\alpha \text{:}k} - \left( {k - 1} \right)}}{\alpha = \frac{\Delta \; {{COR}\left\lbrack {k - 1} \right\rbrack}}{{\Delta \; {{COR}\left\lbrack {k - 1} \right\rbrack}} - {\Delta \; {{COR}\lbrack k\rbrack}}}}} & (3)\end{matrix}$

On the other hand, the integer portion β can be calculated with belowexpression (4), from FIG. 8A.

β+k−1  (4)

It is possible to calculate the focus offset amount PRD from the sum ofα and β that were obtained in the above manner.

Also, in a case where a plurality of zero crosses exist as in FIG. 7B, alocation having a larger steepness MAXDER of the change in thecorrelation amount at the zero cross is used as a first zero cross. Thissteepness MAXDER is an index that indicates the ease of specifying thein-focus position, and indicates that this is a point, where it iseasier to specify the in-focus position when the value of the index islarger. The steepness MAXDER can be calculated with below expression(5).

MAXDER=|ΔCOR[k−1]|+|ΔCOR[k]|  (5)

As described above, in a case where a plurality of zero crosses exist,the first zero cross is determined from the steepness at the zerocrosses.

Next is a description of the method of calculating reliability of theimage signal in step S205. This corresponds to reliability of thedefocus amount, but the calculation method described below is only anexample, and reliability may also be calculated using another publiclyknown method. Reliability can be defined using the above-describedsteepness and a degree of coincidence FNCLVL (referred to below as a‘degree of two image coincidence’) between the A image signal and the Bimage signal. The degree of two image coincidence is an index thatindicates accuracy of the focus offset amount, and accuracy is betterwhen the index has a smaller value.

FIG. 8B shows an enlarged view of the portion of local minimum vicinity602 in FIG. 7A, in which reference sign 608 denotes a portion of thecorrelation amount waveform 601. The degree of two image coincidence canbe calculated with below expression (6).

(i) when ΔCOR[k−1]×2≦MAXDER: FNCLVL=COR[k−1]+ΔCOR[k−1]/4

(ii) when ΔCOR[k−1]×2>MAXDER: FNCLVL=COR[k]−ΔCOR[k]/4  (6)

When focus detection processing as described above ends in step S103,processing proceeds to step S104. In step S104, whether or not thedefocus amount is within a first predetermined range, and reliability ishigher than a first threshold value that was determined in advance, arediscriminated. When the defocus amount is within the first predeterminedrange and reliability is higher than a first threshold value Th_A (Yesin step S104), the focus assist display is set to the first displayformat shown in FIG. 3A (step S105).

The first predetermined range is a range for discriminating whether ornot the position of the focusing lens 103 has entered the in-focus rangefor the subject, and for example, is set based on the depth of focus.Here, the first predetermined range is adopted as the depth of focus.Also, as reliability of the defocus amount, a level such that it ispossible to judge that the accuracy of the defocus amount that wascalculated is certain is set as the first threshold value Th_A. In acase where the defocus amount reliability is higher than the firstthreshold value Th_A, for example, contrast of the A image signal andthe B image signal is high, and in this state the shapes of the A imagesignal and the B image signal are similar (degree of two imagecoincidence is high), or the main subject image is already in focus.

On the other hand, in a case where the defocus amount is outside of thefirst predetermined range, or reliability is the first threshold valueTh_A or less (No in Step S104), processing moves to step S106.

In step S106, whether or not the defocus amount is within a secondpredetermined range, and reliability is higher than the first thresholdvalue Th_A, are discriminated. When the defocus amount is within thesecond predetermined range and reliability is higher than the firstthreshold value Th_A (Yes in step S106), in order to set an index thatindicates a direction and amount to an in-focus state in focus assistdisplay, an index orientation is calculated from the defocus direction(step S107). Then, positions for displaying display parts are calculatedfrom a defocus amount as described later (step S108). Here, the displayparts whose display positions are calculated are the display parts thatmove in the second display format described in FIG. 3B. Then, focusassist display is set to the second display format shown in FIG. 3B(step S109). On the other hand, in a case where the defocus amount isoutside of the second predetermined range, or reliability is the firstthreshold value Th_A or less No in Step S106), processing moves to stepS110.

Note that in the second predetermined range, a defocus amount is setthat can be detected without reliance on the subject. This is because,for example, it is conceivable that the detectable defocus amountdiffers between a high contrast subject and a low contrast subject. Insuch a case, the state that can be displayed in the second displayformat differs depending on the subject, so the user feels uneasy.Therefore, by setting the second predetermined range, an amount is setwhereby a defocus amount can generally be obtained regardless of thesubject. For example, in the present embodiment the defocus amount isset to 2 mm. However, the manner of setting the defocus amount is notlimited to this, and differs also depending on the shift amount whenobtaining a focus offset amount. It is not necessary to set the shiftamount in a case where it is not possible to detect a defocus amountthat exceeds 2 mm, and in that case the second predetermined range maybe infinitely large.

Also, the defocus amount may be determined in consideration ofoperability of the focus assist display. In the second display format,the display parts that move indicate how much the present state isoffset from an in-focus state. Therefore, when performing display to aposition far from the display part fixed at the top, it is difficult forthe user to know how far the present position is from the in-focusposition. Also, depending on the display method, when the size of focusassist display on a screen also becomes large, the screen becomesdifficult to view, so the defocus amount may be determined inconsideration of these matters.

In step S110, whether or not reliability is the second threshold valueTh_B or less is discriminated. When reliability is not the secondthreshold value Th_B or less (No in Step S110), an orientation of theindex of focus assist display is calculated from the defocus direction(step S111), and focus assist display is set to the third display formatshown in FIG. 3C (step S112).

Thus, in a case where reliability is the first threshold value Th_A orless (threshold value or less), and is higher than the second thresholdvalue Th_B (reliability is moderate), it is determined that the defocusdirection indicating the direction that the in-focus position isexpected to exist is certain. Note that a case where reliability of thedefocus amount is the first threshold value Th_A or less, and is higherthan the second threshold value Th_B, is the following sort of state.That is, although the degree of two image coincidence level calculatedwith the focus signal processing unit 204 is less than a predeterminedvalue, there is a definite tendency for the correlation amount obtainedby relatively shifting the A image signal and the B image signal, so itis possible to rely on the defocus direction. For example, the abovedetermination is often made when there is a small amount of blur of themain subject.

On the other hand, in a case where reliability is the second thresholdvalue Th_B or less (Yes in step S110), it is determined that it is notpossible to rely on the defocus amount and the defocus direction. Then,focus assist display is set to the fourth display format shown in FIG.3D (step S113). A case where reliability is the second threshold valueTh_B or less, for example, is state in which the A image signal and theB image signal have low contrast, and the degree of two imagecoincidence is also low. This state often occurs when the subject isgreatly blurred, and so calculation of a defocus amount is difficult.

In step S114, based on any of the first through fourth display formatsthat were set by the above processing, parameters necessary for focusassist display such as color information of focus assist display, andindex orientation and position, are set, and notice of these parametersis given to the display unit 205.

Next is a description of the method for calculating positions of displayparts of focus assist display in step S108 in FIG. 4B, with reference toFIGS. 9A to 9D. In FIGS. 9A to 9D, defocus amount is shown on thehorizontal axis, and display part positions (index position) are shownon the vertical axis. Note that here the index position indicates, as anangle, a movement amount of the display parts that move (display parts301, 305, 307, and 308), with respect to the position of the displaypart that is fixed at the top in the second display format described inFIG. 3B.

If the detection accuracy is constant regardless of the defocus amountthat was detected, when the defocus amount and the index position areexpressed linearly as indicated by dotted line 702 in FIG. 9A, anoperating amount of a focus ring, for example, matches to the displaypositions of display parts, and thus a focus operation is easy toperform. However, in the case of an on-imaging plane phase differencedetection method, as described above, detection accuracy decreases asthe defocus amount increases. Therefore, in a case where a display partwas displayed at a position corresponding linearly to the defocus amountthat was output, it is conceivable that the relationship between theactual focus state and the display part position will vary due to thedecrease in detection accuracy. In this case, the user. sometimes feelsdiscomfort, and operability worsens.

Therefore, in the first embodiment, a configuration is adopted in which,as indicated by solid line 701 in FIG. 9A, movement of the display partposition is made less sharp as the defocus amount increases. That is,the change in position (conversion amount) of the display part relativeto the defocus amount is reduced as the defocus amount increases. Inother words, as the defocus amount increases, the defocus amount thatcorresponds to the position change per unit angle (unit movement amount)of the display part is increased. For example, in the case of focusassist display as indicated by the solid line 701, when the display partposition is indicated as an angle, a defocus amount of 0.02 mm per onedegree is indicated up to a defocus amount of 0.5 mm. Also, a defocusamount of 0.04 mm per one degree is indicated up to a defocus amount of1 mm, and a defocus amount of 0.08 mm per one degree is indicated up toa defocus amount of 2 mm. Also, when one degree is indicated based onthe depth of focus, one degree is indicated as the depth of focus up toa defocus amount of 0.5 mm, two times the depth of focus per one degreeis indicated up to a defocus amount of 1 mm, and four times the depth offocus per one degree is indicated up to a defocus amount of 2 mm. Bycontrolling the index position in this way, it is possible to realizestable focus assist display regardless of the defocus amount.

Next, FIG. 9B illustrates control of the index position according toaperture. As described above, in the case of an on-imaging plane phasedifference detection method, as the aperture changes from a full-openaperture to a small aperture, the focus offset amount of the A imagesignal and the B image signal differs even in cases where a certainsubject was shot at the same distance to the subject. The focus offsetamount is largest and the detection accuracy is highest in the case of afull-open aperture. Therefore, in a case where a defocus amount that hasbeen detected was converted as-is to an index, it is conceivable thatthe relationship between the actual focus state and the display partposition will vary more with a smaller aperture. Therefore, as indicatedby lines 701, 703, and 705 in FIG. 9B, movement of the display partposition is changed according to the aperture. That is, the change inposition (conversion amount) of the display part relative to the defocusamount is reduced as the aperture changes from a full-open aperture to asmall aperture. For example, conversion is performed such that thedefocus amount per one degree doubles when the aperture is F5.6 relativeto when the aperture is F2.8. Thus, it is possible to realize stablefocus assist display regardless of the aperture.

Further, because the depth of focus deepens as the aperture changes froma full-open aperture to a small aperture, the subject becomes lesslikely to blur in comparison to a case where the aperture is on thefull-open aperture side. In this case, it is conceivable that on thesmall aperture side, there is less influence of image collapse in a casewhere the focusing lens was moved from the in-focus position, and sodetection is possible up to a large defocus amount. Therefore, as shownin FIG. 9C, the second predetermined range used in the determination instep S106 in FIG. 4A is widened on the small aperture side indicated byline 704 in comparison to a case of the full-open aperture sideindicated by line 701. By adopting such a configuration, the displaypart movement in focus assist display changes less between the full-openaperture side and the small aperture side for a given image blur. Thus,the display part movement in focus assist display is stabilized for thevideo image viewed by the user, and operability improves.

FIG. 9D illustrates a state of low illuminance and a state of a non-lowilluminance. As described above, in a state of low illuminance, thesignal levels of the A image signal and the B image signal decrease.Also, due to increasing ISO sensitivity a noise component increases andthe S/N ratio decreases, so detection accuracy also decreases. In thiscase as well, it is conceivable that the relationship between the actualfocus state and the display part position will vary. Therefore, in astate of low illuminance, as indicated by line 705, the change in thedisplay part position for a given defocus amount is reduced. Forexample, line 705 indicates that the defocus amount per one degree isdoubled in a state of low illuminance relative to a state of non-lowilluminance.

In the first embodiment, for example, whether low illuminance or not isdetermined using the below four determination methods. In the firstdetermination method, it is determined whether or not ISO sensitivityhas been set to a predetermined value or more. When ISO sensitivity is apredetermined value or more, it is determined that low illuminanceshooting is being performed, and when ISO sensitivity is less than thepredetermined value, it is determined that low illuminance shooting isnot being performed. In the second determination method, it isdetermined whether or not a peak value of luminance of a video signal isa predetermined value or more. When the peak value of luminance of thevideo signal is the predetermined value or more, it is determined thatlow illuminance shooting is not being performed, and when the peak valueof luminance of the video signal is less than the predetermined value,it is determined that low illuminance shooting is being performed. Inthe third determination method, it is determined whether or not anexposure value is a predetermined value or less. When the exposure valueis the predetermined value or less, it is determined that lowilluminance shooting is being performed, and when the exposure value ismore than the predetermined value, it is determined that low illuminanceshooting is not being performed. In the fourth determination method, itis determined whether or not a gain setting is a predetermined value ormore. When the gain setting value is the predetermined value or more, itis determined that low illuminance shooting is being performed, and whenthe gain setting value is less than the predetermined value, it isdetermined that low illuminance shooting is not being performed.

Note that calculation of the display part position in focus assistdisplay according to the above-described states of defocus amount,aperture, low illuminance, and the like may be implemented by anymethod, or may be implemented by combining a plurality of methods.

By thus changing movement properties of the index in focus assistdisplay according to the defocus amount, aperture, and illuminance, itis possible to realize stable focus assist display, and improve useroperability.

Note that it is conceivable that if the display part position that wascalculated as described above is displayed as-is in the display unit 205each time a position is calculated, it will not be possible to realizesmooth index movement, and so the display will appear crude. Therefore,an average value of index positions (or movement amounts from thereference position) that were calculated a plurality of times iscalculated, and notice of that result is given. The number of past indexpositions used to calculate this average value may be changed accordingto the image shooting state, such as the above-described defocus amount,aperture, low illuminance, and the like. For example, an average valueof the past two index positions is used up to a defocus amount of 1 mm,and an average value of the past three index positions is used up to adefocus amount of 2 mm. Also, for example, an average value of a doublenumber of index positions is used on the small aperture side of F11compared to an aperture between a full-open aperture and F11. Forexample, in a state of low illuminance, an average value of a doublenumber of index positions is used compared to a state of non-lowilluminance.

Also, in order to stably express the index of focus assist display, itis conceivable to average the defocus amount used for calculation of theindex position with past defocus amounts, and use that average value.Thus, it is possible to suppress variation in the defocus amount. Bychanging the number of these past defocus amounts to be averagedaccording to the image shooting state, such as the above-describeddefocus amount, aperture, low illuminance, and the like, it is possibleto perform even more stable focus assist display.

For example, an average value of the past two defocus amounts is used upto a defocus amount of 1 mm, and an average value of the past threedefocus amounts is used up to a defocus amount of 2 mm. Also, forexample, an average value of a double number of defocus amounts is usedon the small aperture side of F11 compared to an aperture between afull-open aperture and F11. For example, in a state of low illuminance,an average value of a double number of defocus amounts is used comparedto a state of non-low illuminance.

According to the first embodiment as described above, in an imageshooting apparatus having a focus assist function when performing manualfocus control, a defocus amount and defocus direction within a focusdetection range, and reliability, are detected by performing focusdetection processing of an on-imaging plane phase difference detectionmethod. By changing focus assist display that indicates the defocusamount and defocus direction according to reliability, a stable functionis realized, and it is possible to improve operability. When doing so,by changing display properties of an index of focus assist display thatindicates a movement amount from a current focusing lens position to anin-focus position according to the defocus amount and image shootingstate, a stable index display is realized, and thus it is possible toreduce user discomfort.

Second Embodiment

Next is a description of the second embodiment of the present invention.Note that in display control of focus assist display in the secondembodiment, processing to calculate an index position in focus assistdisplay in step S108 in FIG. 4B differs from the first embodiment.Accordingly, below, differing points will be described, but adescription of configurations of the image capturing apparatus anddisplay control that are the same as in the first embodiment will beomitted here.

Operability is better for a user if movement of display parts in focusassist display changes linearly relative to movement of a focus ring.For example, it is preferable that a movement amount 1001 of a displaypart in focus assist display in FIG. 10A is the same as a movementamount 1002 from point A to point B of a focus ring in FIG. 10B, wherepoint B is the in-focus position. However, in the case of aninterchangeable lens-type image capturing apparatus, ring operability ofthe focus ring differs depending on the attached lens, so operationlinked to movement of the display part of focus assist display isdifficult. Consequently, in this second embodiment, lens information iscommunicated from the lens control unit 106 to the camera control unit207, and based on the lens information, a conversion amount of thedefocus amount per one unit (one degree) of display position of thedisplay part is set.

A first method is to determine the conversion amount depending on lenstype. For each lens type, whether or not a rotation angle of the focusring is large is stored in advance in the camera main body 20, and thetype of the attached lens unit 10 is transmitted from the lens controlunit :106 to the camera control unit 207. Then, the conversion amountfor converting from the defocus amount to the display position of thedisplay part is changed according to the lens type that was obtained.

FIG. 11A is a flowchart of conversion amount setting processing in thefirst method, and FIG. 11B shows an example of a chart of maximumdisplay angles (maximum movement amounts) for lens types (lens IDs).First, in step S301, lens type information is obtained from the lensunit 10 that has been attached. In step S302, a maximum display anglethat is stored in advance in the camera main body 20 is set from thelens type information. In step S303, a defocus amount per one degree ofangle is set from the maximum display angle. For example, in a casewhere a lens has been attached that has a lens ID of 1104 in the chartin FIG. 11B, the maximum display angle is discriminated to be 60degrees. Then a defocus amount per one degree when the defocus amountset in the second predetermined range is expressed with the maximumdisplay angle is calculated. When the second predetermined range has adefocus amount of 2 mm, the defocus amount per one degree is about 0.033mm. This is similarly true in a case where the second predeterminedrange is based on focus depth.

A second method is to determine the conversion amount depending on themaximum defocus amount and the rotation angle when the focusing lens 103has been moved from the near end to the infinite end of the focus ring,and FIG. 11C shows a flowchart of setting processing in the secondmethod. In step S401, the maximum defocus amount and the rotation angleof the focus ring are obtained. In step S402, a defocus amount per onedegree of rotation angle of the focus ring is calculated. In step S403,the defocus amount that was obtained in step S402 is set as a defocusamount per one degree of the display part in focus assist display. Instep S404, an in-focus position, and the angle of the display partposition in the defocus amount of the second predetermined range, arecalculated.

In step S405, it is determined whether or not the angle that wascalculated in step S404 exceeds a maximum angle that has been set inadvance for the index of focus assist display. When the angle exceedsthe maximum angle for the index of focus assist display (Yes in stepS405), a defocus amount per one degree is calculated based on themaximum angle of the index. Here, it is determined whether or not themaximum angle for the index of focus assist display is exceeded, andwhen determined that the maximum angle is exceeded, the defocus amountper one degree is increased. However, conversely, the secondpredetermined range may be set to a defocus amount calculated from thedefocus amount per one degree of angle of the index that was calculatedin step S403 and the maximum angle that has been set in advance for theindex of focus assist display.

In step S108 in FIG. 4B, the defocus amount that was obtained in stepS103 is converted to an index position, based on the defocus amount perone degree of the index that was obtained as described above.

The second embodiment was described as an interchangeable lens-typeimage capturing system, but similar control can also be performed in afixed lens-type image capturing apparatus. In that case, it is notnecessary to transmit lens information from the lens control unit 106 tothe camera control unit 207.

According to this second embodiment as described above, in addition tosimilar effects as the first embodiment, by changing display propertiesof the index of focus assist display using lens information, it ispossible to perform focus assist display that is suitable foroperability of the focus ring. Thus, it is possible to improve useroperability in the image capturing apparatus.

Third Embodiment

Next is a description of the third. embodiment of the present invention.Note that in display control of focus assist display in the thirdembodiment, processing to calculate an index position in focus assistdisplay in step S108 in FIG. 4B differs from the first and secondembodiments. Accordingly, below, differing points will be described, buta description of configurations of the image capturing apparatus anddisplay control that are the same as in the first and second embodimentswill be omitted here.

In general, the depth of focus at the time of focusing on a subjectlocated at a predetermined distance differs depending on the focallength. The depth of focus is deep when the focal length is in the wideangle side, and the depth of focus becomes narrower as the focal lengthapproaches the telephoto end.

In step S104 in FIG. 4B, if the defocus amount is within the firstpredetermined range, it is determined that an in-focus state isattained, however, in a case where the depth of focus is deep, the rangeof distance where a subject located at a predetermined range of distanceis in focus is wide, and a period of time when the first display formatis maintained becomes long with respect to an amount of operation of afocus ring. As a result, it becomes difficult to focus on a point atwhich the subject located at a predetermined distance is most focused.

Accordingly, the first predetermined range is changed with respect tothe focal length. More specifically, as the focal length is changedtoward the telephoto end, the first predetermined range is widened. Forexample, in a case where the focal length is less than 50 mm, then thefirst predetermined range is set to ×0.7 of the depth of focus; in acase where the focal length is greater than or equal to 50 mm and lessthan 85 mm, then the first predetermined range is set to ×0.8 of thedepth of focus; in a case where the focal length is greater than orequal to 85 mm and less than 135 mm, then the first predetermined rangeis set to ×0.9 of the depth of focus; and in a case where the focallength is greater than or equal to 135 mm, then the first predeterminedrange is set to ×1 of the depth of focus.

Accordingly, if the depth of focus changes depending on the focallength, it becomes easier to focus on a position where a subject is mostfocused, and by the virtue of this, the user operability of the imagecapturing apparatus improves.

Similarly, in a case where the depth of focus is deep, a moving amountof the index of the focus assist display becomes small with respect toan operation amount of the focus ring, and a user may feel uncomfortablewhen the focus assist display is in the second display format.

Accordingly, in the calculation processing of index position in thefocus assist display in step S108 in FIG. 4B, the defocus amount per 1•degree of the index in the focus assist display is changed inaccordance with the focal length. For example, in a case where the focallength is less than 50 mm, then the defocus amount per 1 degree of theindex in the focus assist display in the third embodiment may be set to×0.7 of the defocus amount per 1 degree of the index calculated in thefirst and second embodiments; set to ×0.8 of the defocus amount per 1degree of the index in a case where the focal length is greater than orequal to 50 mm and less than 85 mm; set to ×0.9 of the defocus amountper 1 degree of the index in a case where the focal length is greaterthan or equal to 85 mm and less than 135 mm; and set to ×1 of thedefocus amount per 1 degree of the index in a case where the focallength is greater than or equal to 135 mm.

According to the third embodiment as described above, in addition to thesame effects as those of the first and second embodiments, it ispossible to realize focus assist display conforming to operability ofthe focus ring by changing the display characteristics of the index ofthe focus assist display in response to the focal length. By virtue ofthe above, it is possible to improve a user operability of the imagecapturing apparatus.

Other Embodiments

Embodiment(s) of the present invention can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully as a‘non-transitory computer-readable storage medium’) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application Nos.2015-077147, filed on Apr. 3, 2015, and 2016-042829, filed on Mar. 4,2016 which are hereby incorporated by reference herein in theirentirety.

What is claimed is:
 1. A display control apparatus, comprising: a focusdetection unit configured to detect, based on an image signal obtainablefrom an image sensor, a focus state and reliability of the image signal;and a display control unit configured to display in a display unit, whenfocus adjustment is performed by a manual operation, an index thatindicates the focus state that was detected by the focus detection unit,wherein the display control unit changes a display format of the indexaccording to the reliability.
 2. The display control apparatus accordingto claim 1, wherein the focus detection unit detects a defocus amountand a direction to an in-focus position, and the display control unitdisplays, as the index that indicates the focus state, in a case wherethe reliability is more than a first threshold value that has beendetermined in advance, an index that indicates the defocus amount andthe direction.
 3. The display control apparatus according to claim 2,wherein the first threshold value is set to a value for judging whetheror not it is possible to rely on the defocus amount.
 4. The displaycontrol apparatus according to claim 2, wherein the display control unitdisplays, as the index that indicates the focus state, in a case wherethe reliability is the first threshold value or less and is more than asecond threshold value that is less than the first threshold value, anindex that indicates the direction without indicating the defocusamount.
 5. The display control apparatus according to claim 4, whereinthe second threshold value is set to a value for judging whether or notit is possible to rely on the direction.
 6. The display controlapparatus according to claim 4, wherein the display control unit doesnot display, as the index that indicates the focus state, in a casewhere the reliability is the second threshold value or less, an indexthat indicates the defocus amount and the direction.
 7. The displaycontrol apparatus according to claim 4, wherein the display control unitdisplays, in a case where the reliability is more than the secondthreshold value and the defocus amount is outside of a range that hasbeen determined in advance, an index that indicates the defocus amount,fixed at a position that has been determined in advance.
 8. The displaycontrol apparatus according to claim 2, wherein the display control unitperforms display that indicates the defocus amount by performing displayso as to move the index by a movement amount corresponding to thedefocus amount, relative to a reference position.
 9. The display controlapparatus according to claim 8, wherein the display control unit changesa defocus amount that corresponds to a unit movement amount of theindex, according to at least any of the defocus amount that was detectedby the focus detection unit and an image shooting state.
 10. The displaycontrol apparatus according to claim 9, wherein the display control unitperforms control such that, in a case where the defocus amount that wasdetected by the focus detection unit is a first value, the defocusamount that corresponds to the unit movement amount of the index isincreased in comparison to a case of a second value that is less thanthe first value.
 11. The display control apparatus according to claim 9,wherein the image shooting state includes an aperture state, and thedisplay control unit performs control such that, in a case of a firstaperture value, the defocus amount that corresponds to the unit movementamount of the index is increased in comparison to a case of a secondaperture value on a full-open aperture side relative to the firstaperture value.
 12. The display control apparatus according to claim 11,wherein the display control unit performs display such that, in a casewhere the defocus amount that was detected by the focus detection unitis within a predetermined range, the index moves by a movement amountcorresponding to the defocus amount, and the predetermined range is setlarger in the case of the first aperture value than in the case of thesecond aperture value.
 13. The display control apparatus according toclaim 9, wherein the image shooting state includes an illuminance state,and the display control unit performs control such that, in a case of afirst illuminance, the defocus amount that corresponds to the unitmovement amount of the index is increased in comparison to a case of asecond illuminance that is brighter than the first illuminance.
 14. Thedisplay control apparatus according to claim 9, wherein the imageshooting state includes a state of focal length, and the display controlunit performs control such that, in a case of a first focal length, thedefocus amount that corresponds to the unit movement amount of the indexis increased in comparison to a case of a second focal length on a wideangle side relative to the first focal length.
 15. The display controlapparatus according to claim 14, wherein the display control unitperforms display such that, in a case where the defocus amount that wasdetected by the focus detection unit is within a predetermined range,the index moves by a movement amount corresponding to the defocusamount, and the predetermined range is set larger in the case of thefirst focal length than in the case of the second focal length.
 16. Thedisplay control apparatus according to claim 9, wherein a defocus amountthat corresponds to a unit movement amount of the index is determinedbased on a depth of focus.
 17. The display control apparatus accordingto claim 15, wherein the predetermined range is determined based on adepth of focus.
 18. The display control apparatus according to claim 9,wherein the display control unit calculates an average value of defocusamounts that were obtained by a plurality of instances of detection, andbased on the average value of a predetermined number of the defocusamounts, determines the defocus amount that corresponds to the unitmovement amount of the index.
 19. The display control apparatusaccording to claim 18, wherein the display control unit changes thepredetermined number according to at least any of the defocus amountdetected by the focus detection unit, an aperture state, and anilluminance state.
 20. The display control apparatus according to claim19, wherein the display control unit increases the predetermined numberaccording to satisfaction of at least any of a case where the defocusamount is more than a predetermined value, a case where the aperture ison a small aperture side relative to a predetermined aperture value, anda case where illuminance is less than a predetermined illuminance. 21.The display control apparatus according to claim 9, wherein the displaycontrol unit calculates, a plurality of times, a movement amount of theindex relative to the reference position, and based on an average valueof a predetermined number of the movement amounts, determines a positionto display the index.
 22. The display control apparatus according toclaim 21, wherein the display control unit changes the predeterminednumber according to at least any of the defocus amount detected by thefocus detection unit, an aperture state, and an illuminance state. 23.The display control apparatus according to claim 22, wherein the displaycontrol unit increases the predetermined number according tosatisfaction of at least any of a case where the defocus amount is morethan a predetermined value, a case where the aperture is on a smallaperture side relative to a predetermined aperture value, and a casewhere illuminance is less than a predetermined illuminance.
 24. Thedisplay control apparatus according to claim 1, further comprising anin-focus state determination unit configured to set an in-focus range ofthe defocus amount used for determining in-focus state based on thedefocus amount that was detected by the focus detection unit, whereinthe in-focus state determination unit changes the in-focus range inaccordance with a focal length.
 25. The display control apparatusaccording to claim 24, wherein the in-focus state determination unitperforms control such that, in a case of a third focal length, thein-focus range is increased in comparison to a case of a fourth focallength on a wide angle side relative to the third focal length.
 26. Thedisplay control apparatus according to claim 24, wherein the in-focusstate determination unit changes the in-focus range further based on adepth of focus.
 27. An image capturing apparatus, comprising: an imagesensor having a plurality of pixels provided with a plurality ofphotoelectric converters for a single microlens, the image sensorreceiving luminous flux incident through an imaging optical system withthe plurality of photoelectric converters and outputting a pair of imagesignals; and a display control apparatus that comprises: a focusdetection unit configured to detect, based on the par of image signalsoutput from the image sensor, a focus state by performing focusdetection using a phase difference method and reliability of the pair ofimage signals; and a display control unit configured to display in adisplay unit, when focus adjustment is performed by a manual operation,an index that indicates the focus state that was detected by the focusdetection unit, wherein the display control unit changes a displayformat of the index according to the reliability.
 28. A display controlmethod, comprising: performing focus detection to detect, based on animage signal obtainable from an image sensor, a focus state andreliability of the image signal; and performing display control todisplay in a display unit, when focus adjustment is performed by amanual operation, an index that indicates the focus state that wasdetected in the focus detection, wherein in the display control, adisplay format of the index is changed according to the reliability. 29.A computer-readable storage medium storing a program for causing acomputer to execute a display control method, comprising: performingfocus detection to detect, based on an image signal obtainable from animage sensor, a focus state and reliability of the image signal; andperforming display control to display in a display unit, when focusadjustment is performed by a manual operation, an index that indicatesthe focus state that was detected in the focus detection, wherein in thedisplay control, a display format of the index is changed according tothe reliability.